It is common for a motor be used to drive a shaft, which transfers torque from the motor to be used as mechanical energy for driving a pump, ship propeller or any number of other applications.
Many current couplings are provided as separate pieces used to attach the shaft to a hub to which a gear or other device is attached. In cases where torque is to be transmitted between a shaft and a hub or wheel mounted thereon, such as where a hub is mounted on the end of a driving shaft for connection through a flexible coupling to a similar hub mounted on the end of a driven shaft, or where a turbine wheel is mounted on a shaft, any of several attachment means have heretofore been used; however, each presents problems.
A straight keyed shaft connection comprises keyways cut into the shaft and into the side of the central hole of the hub or wheel; the keyways are radially aligned and a key is inserted to lock the hub or wheel to the shaft. In high speed and high torque applications where extremely tight fits between the interconnected components are important, the required tightness is usually achieved by making the bore in the hub or wheel slightly smaller than the diameter of the shaft, expanding the hub or wheel by the application of heat, slipping the hub or wheel onto the shaft, and allowing it to cool and contract over the shaft resulting in a very tight interference fit with the shaft. This type of connection has several disadvantages. For one, the keyway cut into the shaft produces high stress concentrations which are aggravated with the use of heat for shrink-fitting the hub or wheel on the shaft. The need for precise tolerances in the keyways makes manufacturing difficult and frequently time consuming. Where heat is used to produce a shrink fit, the torches or special heaters required can present a hazard, depending on the environment in which the assembly is carried out.
Tapered key shaft hubs are sometimes used because by making a taper in the bore, a hub can be tightened on a shaft by rotating a nut threaded onto an extension of the shaft which protrudes past the hub. That is, the threaded engagement is used to draw the hub over the tapered portion of the shaft. However, it is extremely difficult to accurately machine a tapered bore and to match bores between shaft and hub, making this type of connection expensive and difficult to consistently achieve. Further, a tapered shaft hub also has the disadvantage that stress concentrations can occur in the keyway, greatly reducing the effective strength of the connection.
Both types of keyed shaft connections generally require torch heating for removal.
An alternative to such an arrangement is disclosed in U.S. Pat. No. 5,123,772, which teaches a coupling in which the hub itself is configured to act as the clamp. While this clamping arrangement operates in a largely satisfactory manner in many cases, these and other clamps of this style can be challenging due to difficulties sometimes associated with precision machining of the meshing threads. Furthermore, in large scale applications, significant part weight of the clamp renders handling more difficult during manufacture, particularly when performing quality checks to confirm the accuracy of the threading.
These and other drawbacks are found in current assemblies for connecting a hub to a shaft.
What is needed is a hub clamp that can provide improved handling during manufacture and subsequent assembly.